I can receive mail and send mail from Windows Outlook
From new MAC with Leopard Mail I can receive mail but cannot send. Spent hours on the phone with Apple and with RoadRunner (BrightHouse Cable) No joy - They both insist that it is the others fault. I found lots of online problems with MAC SMTP going "offline" and not sending - same problem I have, but no real solution.
I deleted mail program and user plist files and reinstalled mail and user settings
Held my tongue to the left and the right - No sucess - Four hours.....